Automatic variable speed gear



Jan. 25, 1938. E. JACQUES AUTOMATIC VARIABLE SPEED GEAR Filed Aprjil 20,19256y '2 -Sheets-Shee't` l Jan. 1938. EJACL'IS 2,106,603

' AUTOMATIC VARIABL SPEED GEAR Filed April- 20, 1936 f 2 Sheets-SheetPatented 25, 1938 UNITED STATES PATENT oFFicE Application April zo,193s, serial 16.575.257 AIn France April 27, 1935 1l claim. (ci.'i4-259) The present invention relates to a speedchanging device,particularly applicable to mo-v tor vehicles and the like and enablingthe speed of the driven shaft to be automatically varied 5 as a functionof the reaction torque, and in inverse ratio thereto, the engine torqueand the speed of the driving shaft being maintained at a constant value.In particular, the invention refers to a variable speed device of thetype having l what may be called a receding reaction point,

in which the point of application of the torquereaction of the reductiongears is constituted by a member adapted to slip against an externalresistance when the resisting torque exceeds a l certain value.

Variable gears of this type are already known,

which comprise a dlierential gear with sun wheels integral with thedriving and driven shafts respectively, the planetary cage being sub-.20 jected to a variable braking torque, as ,a function of the reactioneffort and immobilizing said cage so 4long as the resisting torque isless than or' equal to the driving torque, whilst allowing it to turnmore or less rapidly when the resisting ,2'5 torque exceeds the drivingvtorque, and thereby effecting a reduction in the speed of the drivenshaft. In any event,l the braking torque applied to the planetary cage,absorbs an amount ofpower which is proportional to the speed reductionobtained, and is entirely wasted. To recover this wasted power, it hasbeen proposed to eifect the by means of a generator--hydraulicv orelectric-coupled to the planetary cage in thedifferential and feeding amotore-hydraulic or electric--xed on the driven shaft of the trans- 1125pense with the employment of such a complicated recuperating system, byreducing the losses of power due to the shifting of the recedingreaction point; and it is characterized by the fact that-instead oftending to immobilize the mem- 50 ber serving as the reaction point-theexternal resistance is formed by a slipping clutch located between tworotating members. of the device,

these being connected respectively to the driving and driven members bytransmission means which f ss are so arranged that as soon as slippingoccurs.-

their relative rotational velocity is very low in comparison with therelative velocity of the said driving and driven members.

For example, in a simplified embodiment. the f device according to theinvention .is constituted 6 by a differential with a high reductionratio and whose smaller sunwheel is integral with the driving shaft andwhose larger sun wheel is integral with the driven shaft: and havinginterposed between the sun wheel carried.- by the 10 driven shaft andthe planetary cage a clutchfor example, magnetlc,adapted to transmit atorque equal to the maximum resistance torque for which the device isdesigned.

By way of example, two embodiments of a del5 vice according to theinvention are described below, and illustrated in the accompanyingdrawings.

Fig. 1 is a atie representation ,of the first embodiment; and Fig. 2 isasimilar rep- 2n resentation of the second embodiment.

l Figs. 3 and 4 represent in longitudinal section, two variants indetail of an embodiment of thedeviceinmg.2.

Fig. 5 is theelectrlc circuit diagram for the 25 case in which magneticclutches are used.

The-device shown in Fig. 1 comprises, between the driving shaft I andthe driven shaft 1, a differential of 'which the sun wheel 3, is fast onthe drivingl shaft l, and the orbit wheel-I issu iast on the drivenshaft 2. The said differential has avery high reduction ratio, that`isvto say, I the diameter of the sun wheel l is much-less than that ofthe orbit wheel I, these two wheelsbeing connected by trains of doubleplanet -pin- '35 lons 5, Gand 5', 6', of which the planets i, I'.'meshing. with the sun wheel 3 have a greater diameter than the planets6, 6' meshing with thedriven orbit wheel I. In the example shown thediiferential has spur gearing: the shafts 1, 'i'carrying the pairs ofplanets are parallel with the driving and driven shafts, and the orbitwheel 4 consists of a crown wheel with internal teeth. The differentialmay equally wellbe constructed with bevel gearing. Between the drivenorbit wheel I and the planetary cage l, is disposed a clutch 9(preferably magnetic) adapted 'to transmit when slipping a torqueexceeding the value of the driving torque,l which must be kept constant,and equal to the maximum value so of the resisting torque for which theapparatus is intended.

The device operates 'as follows. When the clutch`l is energized. so longas the resisting 'torque applied to the shaft 2 is less than or" lili.

lI, no slip takes place and the differential rotates as a solid unit andcauses the shaft 2 to be driven at the same speed-as the shaft I.sisting torque exceeds the driving torque, the clutch 8 begins to slipand the planetary cage 8 moves relatively to the driven orbit wheel 4whose speed decreases and becomes inversely proportional to the value ofthe resisting torque.

The operation and advantages of the device according to the inventionare explainable in the' following manner.

Let Ni represent the constant speed of the driving shaft I; N2 the speedof the driven shaft 2; N the speed of the planetary cage 8; k the speedreduction coeilicient of the differential, and n the ratio between themaximum value of the variable resisting torque Cr and the constant valueCn of the driving torque; so that the clutch 8 is able to transmitatorque equal to nCu.

'Ihe ratio between three speeds N, Ni and N2 is given by the equationWhen thedriven shaft 2 tends to be arrested by a resisting torquegreater than the driven torque-Cn, the planetary cage 8 tends to rotateat the speed so that there is available on the planetary cage 8, atorque equal in value to OuUc--l), the result being that the cage ltends to take with it which this clutch can transmit. It is thus evidentthat the device is substantially different fromthe known devicesmentioned earlier in this description in that the external resistanceprovided by the clutch 8 acts. not as a brake, but as a means oftransmission, and the planetary cage is not a braked, but a drivingmember.

- The high efficiency of the device is explainable as follows. It isclear that the maximum loss of power will occur when the driven shaft 2is completely arrested by a resisting torque of` higher value than nc.This lost powernwill clearly amount to nCgNl k+1 Since; on the otherhand, yfthe power applied NXXICH:

4to the device by the driving shaft 'is equalto When the reof only5%,which To enable the device to function in reverse, a second clutch I0 is located between the planetary cage 8 and the frame I I, thede-excitation of the clutch 9 and the excitation of the clutch I0clearly causing a reversal of direction of rotation of the shaft 2. Theclutch `III should be so designed as to allow no slip with the resultthat, in reverse drive, the device operates with a /flxed reductionequal to k.

The arrangement shown diagrammatically in Fig. 2 consists as before of adifferential with a high reduction ratio, the smaller sun wheel 3 beingkeyed on the driving shaft I, whereas the larger orbit wheel 4 is keyedon the driven shaft 2 and the planets 5, 5' mesh simultaneously with thesun Wheel 3 and the orbit wheel 4. Instead of disposing the slippingclutch between the driven orbit wheel 4 and the cage carrying theplanets 5, 5', this clutch 9 is disposed between the orbit wheel 4 andan internally toothed crown wheel I2 mounted idly on the driving shaft Iand the teeth I3 .of which mesh with pinions I4, I4 keyed on the planetshafts I5, I 5'. The crown wheel I2 performs the function of the cage 8in the construction shown in Fig. 1. The ratios of the gears 5-4 andI4-I3 diier, but are very close so that when slipping of the clutchoccurs, the relative speed of the crown wheel I2Y and the orbit wheel 4is extremely low, even when the speed of the latter slows downconsiderably under the effect of a heavy resisting torque applied to theshaft -2.

The advantage of this form of construction resides in this, that thesupplementary reduction represented by the gearing I4-I3, disposedbetween the planetary cageand the slipping means 8, allows thedimensionsof the pinions to be reduced, a lower reduction ratio for thedifferential properly so called, being employed.

In -the example shown in detail in Fig. 3, the driven orbit wheel 4,instead of being -keyed directly on the driven shaft 2, is connectedwith said shaft through a supplementary reduction device which, on theone hand, enables a smoother start to be effected and, on the other,facilitates adapting the runningof the engine to the conditions underwhich the yvehicle is being used (town, road, hills etc.) and alsoallows engine braking at a reduced speed. This auxiliary reductiondevice may also have a reduction ratio varying automatically with theresisting torque applied to the driven shaft, for which purpose itlcomprises a dierential, of which one sun wheel I8 is integral with theorbit wheel 4, and whereof a disc 2| which can be heldsolid, with a disc23 keyed on the driven shaft 2, by means of a magnetic clutch 22.Another clutch 22' enables the disc 2| to be held solid with the fixedhousing 24. Finally, for reversed running, clutch I0 as before enables ad isc 25 to be held solid with the housing 24, the disc 25 beinerintegral with the cage 8 carrying the planet pint ons 5, I4, 5', I4' ofa differential, which is free on the driving shaft I.

The auxiliary reduction device may alsotake arcanos trols of the severalclutches. A lever 3| enables either the clutch 9 (for forward running),or the clutch lll` (for reversing) to be connected to a battery 32, orto the dynamo 33. A manually operated switch 34 serves for energizingeither the.

clutch' 22 of the auxiliary reduction 'device-*for use in trailic or theclutch 22' for hillwork which also allows of engine braking. Theenergizing of these two Vcoils 22, 22', is also controlled by the brakepedal 35 of the vehicle, through the agency ofthe movable sector 36, inconstant connection with the battery, and of the contacts 31, 38respectively connected with the windings 22, 22'. This control allowsbraking and progressive resumption of drive to be effected irrespectiveoi' the running condition (traffic or hill work), se-

lected by means of the switch 3l. What I claim is:-

Automatic change speed mechanism whose 3 speed reductiqnr ratio is afunction o! the resist-- ing said two wheels: a disc mounted idly on thev driving shaft and including an internally toothed crown gear, pinions'integral with the said planet pinion means-and engaging said crowngear, the

tooth ratio oi'- said pinionsand crown gear being di'erent from, butclose to the tooth ratio of the planet'pinion means and thel orbitwheel, and a slippable clutch operative between said disc and the orbitwheel, said clutch being adapted .to

J transmit when slipping a torque equal to the to the driven shaft.

maximum torque applied EMILE JACQUES.

